Air-compressor



(No Model.)

' B. HILL.

AIRCOMPRESSOR. No. 439,876. K Patented Nov. 4, 1890.

mi NORRJSJETERS cm, woTo-u'rnm, vusnmcrou, o. c.

U NITED STATES PATENT OFFICE.

EBENEZER HILL, OF SOUTH NORWVALK, CONNECTICUT.

AIR-COMPRESSOR.

SPECIFICATION formingpart of Letters Patent No. 439,876, dated November 4, 1890.

Application filed May 19, 1890. Serial No. 352,356. (No model.)

To aZZ whom it may concern:

Be it known that I, EBENEZER HILL, of South Norwalk, in the county of Fairfield and State of Connecticut, have invented a new Improvement in Air-Compressors; and I do hereby declare the following, when taken in connection with accompanying drawings and the letters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this specification, and represent, in

Figure 1, a longitudinal central section of a compressing-cylinder and side view of the auxiliary or minimum-pressure receiver in connection therewith; Fig. 2, a modification in the arrangement of the minimum-pressure valve.

This invention relates to an improvement in air-compressing apparatus.

In many cases where aircon1pressors are used different pressures are desirable. Especially is this the fact in mining where compressed air is used as a power to drive the drills. The pressure of the air for this purpose must ordinarily be from sixty to one hundred pounds, whereas as a blast for blacksmiths fires, spraying of oil for boiler-fires, and other purposes a very much lighter pressure is desirable; but the usual construction of air-compressor necessitates compressing the air to the maximum pressure required and then the discharge throttled to bring it to the lower pressure required. The result of this is a very considerable waste of power.

The object of my invention is the construction of an apparatus whereby two different pressures may be obtained from the same apparatus without throttling-that is, so that a certain portion of the air may be discharged at the minimum pressure while the remain der will be discharged at the maximum pressure.

To this end the invention consists in the arrangement of an outwardly-opening valve midway of the stroke of the piston, combined with a receiver and a connection therefrom to the said valve-chamber, and whereby the air during the first part of the stroke of the piston will be forced through the said valve into the said receiver while the latter part of the stroke of the piston will compress the air then in the cylinder to the maximum extent desired, that in the said receiver standing at the minimum pressure required.

In the illustrations, A represents the cylinder of a common'air-compressor, and B the piston arranged to work therein in the usual manner, and the cylinder is provided with suit able valves for inlet and outlet of the air at the respective ends of the cylinder, also in the usual manner. Through the cylinder and midway of the stroke of the piston apassage C opens outward, the said passage being normally closed by a spring-valve D, which operates as an outlet-valve for the escape of air and a check-valve to prevent the return of the air. Hence this valve is preferably provided with a spring E, the tendency of which is to yieldingly hold the valve in its closed position.

F represents a receiver adapted to receive air at the lower or minimum pressure from the valve-chamber. A tube G leads to the receiver, so that air which may pass out through the passage C will be conducted to the receiver F, and from which air may be drawn through a valve 11 or otherwise, as required. The outlet-valves at the end of the cylinder communicate with an independent receiver adapted to receive the air at the maximum pressure required. The air in this case passes out through a passage I to the receiver in the usual manner. The receiver for this maximum pressure is not shown.

The operation of the apparatus is as follows: Supposing the piston to stand at the right, as represented in the drawings, and to move from that position toward the left. Under such movement the air within the cylinder being compressed will raise the valve D and permit the air to escape through the passage C and pass into the receiver F until the piston has passed the passage Cthat is to say, the air will escape through the passage C to the receiver F during the first part of the movement of the piston; but after the piston has passed the passage C there is no escape except through the outlet-valve at the end of the cylinder to the principal receiver or receiver of the maximum pressure, and the air remaining in the cylinder after the piston so passes the passage 0 will be compressed to this higher or maximum pressure and be delivered to the maxim rim-pressure receiver. On the return of the piston a like operation will be produced, assuming the compressor to be a double-acting compressor.

It is well known that when the piston of the air-compressor has passed through one-half its stroke the pressure in front of the piston has reached about fifteen pounds. Hence air will pass through the valve B into the receiver automatically at this pressure of about fifteen pounds, which is the minimum pressure required for the purposes of a blast, spraying oil, &c. Consequently the arrangement of a single passage and valve in the cylinder midway of the length of the stroke of the piston will produce the required result, delivering the requisite supply of air for the minimum pressure to the receiver F and then air of the maximum pressure to the other receiver; but should a higher pressure be desirable than the fifteen pounds, then the valve will be arranged nearer one end of the cylinder than the otherthat is to say, the arrangement of the valve midway of the length .of the cylinder producing, as suggested, a

pressure of fifteen pounds, because the air will escape until the piston passes the valveopening, and the air will be compressed from v that point onward. If therefore a greater pressure is desirable, the valve will be arranged proportionately farther from the end of the compressing-stroke of the piston, so that the piston will sooner pass the escapevalve opening and will then operate upon a correspondingly greater amount of air. The position of the said valve will therefore be made with relation to the piston, according to the pressure required. In case of a double-acting compressor two valves would be thus arranged, opening to a common passage, as seen in Fig. 2,the air escaping through the passage nearest the end of the stroke of the pistonsthat is, through one passage as the piston moves in one direction and through th other passage as it moves in the opposite direction. By this construction of apparatus I am enabled to produce from the same compressor both the maximum and minimum pressures without the necessity of first compressing the air to the maximum pressure and then reducing that pressure by throttling or otherwise for specific purposes.

I do not illustrate the mechanism for driving the pistons, as this is too well known to require illustration or description.

I claim In an air-compressor, the compressing-cylinder provided with the usual outlet and inlet valves constructed with one or more passages opening outward midw'ay or between the extreme positions of the piston, a valve adapted to close said passage,but opening outward, an air-receiver, and an open connection from the chamber of the said valve to the said receiver, substantially as described, and whereby the said receiver will be supplied with air at a pressure lower than the maximum pressure of the cylinder.

EBENEZER HILL.

Witnessesi J. E. SLATER, H. P. MORGAN. 

